How do I get my shell functions to make use of existing autocompletion in zsh?

Question

I have a couple of shell functions defined in my .zshrc which save on typing and allow integration with screen. For example:

function s()
{
 screen -t "1ドル" ssh "$@"
}

However, when I use these shell functions, I can't take advantage of zsh's built in command completion features. (In the case of SSH, automatically completing hostnames based on known_hosts and ssh_config). What's the preferred way to hook in to the existing completion mechanisms for commands I've created wrappers for?

EDIT:

Thanks to Gilles for his answer below. Using compdef appears to be the way to do this, but interestingly it doesn't seem to work uniformly. In this case, I have the following setup:

function s()
{
 screen -t "1ドル" ssh "$@"
}
function m()
{
 screen -t "man.1ドル" man "1ドル"
}
compdef $_comps[man] m
compdef $_comps[ssh] s

Completion for my wrapper function 'm' works as expected, however completion for my function 's' does not; rather than attempting to complete hostnames, it appears to fall back to default autocompletion by providing me a list of files when I hit 'tab'. Is there some oddity in the way that SSH completion is handled which means I need to do something further?

Answer 1

To request that a command be completed like another command that is already known to the completion system, you can use the compdef my_command=known_command form of compdef.

compdef s=ssh
compdef {cxterm,uxterm,xterm-color}=xterm

Under the hood, this is basically equivalent to _comps[s]=$_comps[ssh].

Some completion commands apply to a family of functions and read the first word of the command line to determine which particular command to complete. For example, the commands ssh, scp, sftp and a few more are all completed by the function _ssh. In that case, you need to tell the completion function which "service" your function is like (by default, the service is the executable name, here your function's name).

_s () {
 local service=ssh
 _ssh "$@"
}
compdef _s s

• Murali Suriar: Thanks - I assumed compdef was what I wanted to use. Out of interest, is there any reason you create a local variable and shift, rather than referencing 1ドル and 2ドル in your call to compdef?
• Gilles 'SO- stop being evil': @Murali: That's so I can write something like compdefas xterm cxterm uxterm xterm-color.
• Murali Suriar: interesting - so I've defined two wrappers, one for 'man' and one for 'ssh'. Using compdef, completion for my 'man' wrapper works, but completion for my 'ssh' wrapper doesn't. Have you run into any issues like this before? Is there something else I have to poke in order for _ssh to work with my alias/wrapper?